WASHINGTON -- NASA's Dawn spacecraft has provided researchers with thefirst orbital analysis of the giant asteroid Vesta, yielding newinsights into its creation and relation to the terrestrial planetsand Earth's moon.

Vesta now has been revealed as a special fossil of the early solarsystem with a more varied, diverse surface than originally thought.Scientists have confirmed a variety of ways Vesta more closelyresembles a small planet or Earth's moon than another asteroid.Results appear in today's edition of the journal Science.

"Dawn's visit to Vesta has confirmed our broad theories of this giantasteroid's history, while helping to fill in details it would havebeen impossible to know from afar," said Carol Raymond, deputyprincipal investigator at NASA's Jet Propulsion Laboratory (JPL) inPasadena, Calif. "Dawn's residence at Vesta of nearly a year has madethe asteroid's planet-like qualities obvious and shown us ourconnection to that bright orb in our night sky."

Scientists now see Vesta as a layered, planetary building block withan iron core - the only one known to survive the earliest days of thesolar system. The asteroid's geologic complexity can be attributed toa process that separated the asteroid into a crust, mantle and ironcore with a radius of approximately 68 miles (110 kilometers) about4.56 billion years ago. The terrestrial planets and Earth's moonformed in a similar way.

Dawn observed a pattern of minerals exposed by deep gashes created byspace rock impacts, which may support the idea the asteroid once hada subsurface magma ocean. A magma ocean occurs when a body undergoesalmost complete melting, leading to layered building blocks that canform planets. Other bodies with magma oceans ended up becoming partsof Earth and other planets.

Data also confirm a distinct group of meteorites found on Earth did,as theorized, originate from Vesta. The signatures of pyroxene, aniron- and magnesium-rich mineral, in those meteorites match those ofrocks on Vesta's surface. These objects account for about 6 percentof all meteorites seen falling on Earth.

This makes the asteroid one of the largest single sources for Earth'smeteorites. The finding also marks the first time a spacecraft hasbeen able to visit the source of samples after they were identified on Earth.

Scientists now know Vesta's topography is quite steep and varied. Somecraters on Vesta formed on very steep slopes and have nearly verticalsides, with landslides occurring more frequently than expected.

Another unexpected finding was that the asteroid's central peak in theRheasilvia basin in the southern hemisphere is much higher and wider,relative to its crater size, than the central peaks of craters onbodies like our moon. Vesta also bears similarities to otherlow-gravity worlds like Saturn's small icy moons, and its surface haslight and dark markings that don't match the predictable patterns onEarth's moon.

"We know a lot about the moon and we're only coming up to speed now onVesta," said Vishnu Reddy, a framing camera team member at the MaxPlanck Institute for Solar System Research in Germany and theUniversity of North Dakota in Grand Forks. "Comparing the two givesus two storylines for how these fraternal twins evolved in the earlysolar system."

Dawn has revealed details of ongoing collisions that battered Vestathroughout its history. Dawn scientists now can date the two giantimpacts that pounded Vesta's southern hemisphere and created thebasin Veneneia approximately 2 billion years ago and the Rheasilviabasin about 1 billion years ago. Rheasilvia is the largest impactbasin on Vesta.

"The large impact basins on the moon are all quite old," said DavidO'Brien, a Dawn participating scientist from the Planetary ScienceInstitute in Tucson, Ariz. "The fact that the largest impact on Vestais so young was surprising."

Launched in 2007, Dawn began exploring Vesta in mid-2011. Thespacecraft will depart Vesta on August 26 for its next study target,the dwarf planet Ceres, in 2015.

Dawn's mission to Vesta and Ceres is managed by JPL for NASA's ScienceMission Directorate in Washington. Dawn is a project of thedirectorate's Discovery Program managed by NASA's Marshall SpaceFlight Center in Huntsville, Ala. UCLA is responsible for overallDawn mission science. Orbital Sciences Corp. in Dulles, Va., designedand built the spacecraft. The German Aerospace Center, the Max PlanckInstitute for Solar System Research, the Italian Space Agency and theItalian National Astrophysical Institute are international partnerson the mission team.